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Ball Bearings
right|Yo-yo ball bearings __TOC__ Ball bearings, in the context of yo-yo play, are used to reduce friction while the yo-yo is sleeping. A so called ball bearing yo-yo can be played in two extreme states. One configuration involves using a thick lubricant in the ball bearing, so that sleep times will be low. This configuration is generally used for looping tricks. The second configuration involves cleaning the ball bearing of any lubricant - playing a "dry" bearing. Dry bearings are usually used in yo-yo's meant to perform string tricks. Anatomy As the cross section diagram shows, a ball bearing consists of an outer race (top blue bar), an inner race (bottom blue bar) and balls (grey) that roll in grooves in the races. To keep the balls evenly distributed, some bearings employ a so called cage (green). Since dust inside of the bearing is quite detrimental to its performance, the side walls are often protected by shields (red) that are fixed on - and rotate with - the outer race. The shields can usually be removed by taking out the small steel springs that hold them in place. In a yo-yo, the bearing is mounted around an axle (light grey) and gripped on the sides by shims (yellow). Since the shields rotate with the outer race, it is very important, that the shims do not touch the shields. Many players remove the shields permanently to prevent this, and to allow easier cleaning and inspection. Materials * Steel - Historically, most yo-yo ball bearings have been made from steel. Some are stainless, but since stainless steel is much softer than ordinary steel, this reduces the life time of the bearing. That's why many manufactures (like BuzzOn) use non-stainless bearings. * Ceramic - A more expensive variety use ceramic silicon nitride balls inside, but retain a stainless steel race and exterior. * Gold - The gold bearing commissioned by Taka in Japan initially showed promise of being even better than the ceramic bearings. However, these bearings have shown a decrease in performance in a relatively short period of time after using them in a yo-yo. The quality of a bearing is sometimes given in ABEC numbers. These numbers refer to a scale of roughness of the ball surface, which results in a recommended maximum rpm for a bearing. Usually yo-yo bearings come as ABEC-3, smoother ones as ABEC-7. Maybe someone can shed some light on how significant this difference is in yo-yoing. I remember reading a post in a skating newsgroup where an engineer claimed it was all just a marketing gag and that the difference between an ABEC-3 and an ABEC-7 bearing would start to be noticeable at speeds exceeding 200mph. :-) Special Bearings Over the years there have been a few innovations in ball bearings specially geared towards the yo-yo market. KonKave The KonKave Bearing was developed by Dif-e-Yo. The intention here is to keep the string centered on the bearing and away from the response system. The outer surface ouf these bearings is (as the name implies) not flat, but slightly concave. Earlier experiments by Dif-e-Yo included a grooved bearing, where the string was kept in a groove running around the outer race. Most Dif-e-Yos come with a KonKave already installed. For many other yo-yos Dif-e-Yo offers conversion kits, the process of upgrading an existing yo-yo thus became known as KonKaving. Mercury Another novel variety of bearing is the mercury bearing. These were first introduced into the main-stream yo-yo hobby market by Infinite Illusions. The mercury bearings, named after the Greek god Mercury, do not contain any elemental mercury. What makes the mercury bearing special is the factory cleaning process which increases spin time and decreases response. Mercury Fat Lip These are normal Mercury bearings (see above) that have a wider inner race. This is to make sure that the shims cannot touch the shields. Care To get the most out of your ball bearing, it requires some care. Breaking In A bearing usually does not perform perfectly out of the box, they need some breaking in. This can usually be achieved by throwing a few long sleepers. Some players stick their bearings on the tip of an electric drill in order to break it in, hence the saying "to dremel a bearing". Cleaning * See article Cleaning a Bearing. Lubricating Bearings usually run best, when they are dry, i.e. all lubricant has been cleaned out of them. This gives them nearly no response at all. The downside of this is a reduced life span (can someone please relate from their own experience, what can be expected), the possibility of rusting, as well as more noise, and I mean NOISE as in really, really noisy :-). Alternatively bearings can be slightly oiled with a thin lubricant (aka Thin Lube). This keeps them from rusting and from being too noisy. It also gives them slightly more response. Trumpet valve oil is one example of a thin lube that makes the bearing nearly as unresponsive as a dry bearing. Most yoyo stores however now offer yoyo specific thin lube. For yoyoers who want more response for looping yoyos, a thick lubricant is used in much greater quantities. This is most commonly seen in AA play. This makes the ball bearing nearly as responsive as a fixed axle, but with longer sleep times. Types of thick lubricants include petroleum jelly and 3-in-1 oil. This is usually applied without cleaning to the outside of the shields, to give them more friction against the yo-yo halves.